The real problem isn't that exams are dumbed down – it is that we rely so much on them

We've got a terrific scoop in the newspaper this morning. It turns out that not only are A-levels and GCSEs getting easier, teachers are being trained how to teach them by the very people who set the papers. For £230 a day, chief examiners will explain exactly how pupils' papers are marked, how to word answers, and, most worryingly, which compulsory questions are likely to come up in that year's papers. “We’re cheating,” says one chief examiner. “We’re telling you the cycle [of the compulsory question]. Probably the regulator will tell us off.”

What's most tragic about this story is that it's only the last part – the "cheating" – that is genuinely surprising. It is already relatively well known that examiners look for a certain type of script, especially in humanities. They issue guidance papers and mark schemes which anyone can download or buy. When I took my A-levels, I had one history teacher who knew exactly how this worked – every essay on Hitler had to be "pragmatism versus ideology", or some such variation. Tick the boxes and you'll be OK.

This is awful, but unfortunately almost inevitable. Each year, hundreds of thousands of pupils take A-levels, GCSEs and so on. They produce mountains of exam scripts, all of which have to be marked. The markers are mostly overworked teachers, many hastily trained and dragged out of the classroom. If you gave them the discretion to mark based on their own assessments, an A from one marker might not equal an A from another. Pupils and teachers would begin to worry about whether their scripts had been "unfairly" marked. Parents would attack teachers for not teaching the exam properly. The number of appeals would rocket.

The real problem isn't that the exams are easy – it is the incentives they create. Schools are judged entirely on league tables, and so have every incentive to teach to the exam. For the Government, exam results are proof of how great their policies are, and so they too want them to go up. For pupils, exam results are the key to getting everything from a job at McDonald's to a place at a good university. And as we now know, for exam boards, meeting these needs is profitable. We have made a fetish out of exam results – we use them to judge pupils, teachers and schools – and as any economist knows, any test you make that important is likely to fail.

But ultimately, exams don't exist for schools, politicians or for pupils – they exist for the universities and employers which have to rely on the results. Neither has an incentive for results to be systematically inflated – more qualifications can't increase the number of jobs or places, after all. The best solution is to allow them to set their own tests. To a degree, this is already happening. At Oxford pupils now have to take the HAT (the history admissions test), or the LNAT (for law), or the ELAT for English. The difference between these tests and A-levels is that the admissions tutor actually gets to read the script, and to interview the candidate who wrote it.

So, we should get rid of nationalised tests as quickly as possible, and instead let schools teach what their pupils (and their parents) want to learn. Make schools directly accountable to their users, rather than to league tables. Free parents to send their children where they like. And let the people who need them set the tests. Only then will this corruption be stamped out.